In a variable displacement engine, fuel efficiency tends to increase when fewer than all cylinders are activated. Pumping work that would have been performed by a deactivated cylinder on an intake stroke of a four-stroke cycle is temporarily reduced significantly, thereby reducing fuel consumption and improving fuel efficiency at low engine loads and/or speeds. When operating conditions are such that higher engine torque is called for, all cylinders may become activated to supply the demand.
In a vehicle in which cylinder deactivation is implemented, typically half the total number of engine cylinders, e.g., every other cylinder in a vehicle firing order, are deactivated. There are limits, however, to deactivating cylinders to improve fuel efficiency. For example, vehicle noise and vibration tend to increase when more than half the total number of engine cylinders are deactivated.